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Orange peel

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  • Orange peel

    I just went through my first powder coating project. I'm using the Harbor Freight gun system and a normal kitchen oven that I use outdoors just for powder.

    I applied some high gloss black powder to some 68 pontiac hood scoop inserts (I think they are cast peices...not sure though). I cured the pieces at 400F for 10 minutes as specified and ended up with horrible orange peel....I sanded with 1500 wet and still couldnt get rid of the peel.

    The oven was soaking at 400F for 30 minutes prior to parts being inserted. I let the parts cool in the oven with door propped open and oven shut off.

    I prepared the parts by sanding to bare metal with 220 grit and then cleaning with laquer thinner.

    When I applied the powder, I believe I got good adhesion because the powder attached itself to the parts with great uniformity.

    So, after my first attempt with the bad orange peel...I sanded the black powder coat with 400 grit wet and heated the parts for a while with a hand held heat gun and finally I reapplied the black powder coat. I used the same cure process and achieved better results than the first attempt...but there was still orange peel present.

    So now I have stripped the parts back to bare metal and I await some suggestions from u guys on what I could be doing wrong.

    Any opinions or help you can offer is appreciated.

    Unfortunately, I bought the powder of of eBay (from an individual not a company) so I cant be caertain of its origination or quality.


  • #2
    I can't be sure because we don't know the origin of your powder, but it sounds like maybe it was under-cured and didn't have enough time to flow out. Caswell powders have a cure rate of 400 degrees at 14-15 minutes. I have the same Harbor Freight powder gun, and have used Caswell powders from the beginning. I've had excellent results with smooth glossy finishes. Try curing a little longer and see if it helps. Use an oven thermometer from the local hardware store. If your part will cure near the oven floor, put the thermometer near the floor too. Practice on a few pieces of scrap metal so you don't have to repair any experiment gone bad.

    Sandblasting is probably a quicker and easier way of prepping your parts. It also gives the powder a good surface to adhere to. It's possible that something in the laquer thinner could be contributing to the orange peel, but I still think it may just be under-cured.



    • #3
      Do you have an inline oil/water separator from your air compressor to your gun? If not, you may want to invest in one. I did, and it took care of a lot of my orange peel problems.


      • #4
        Lower your oven temp to 325 to 350 and still bake for 30 min then open door and let cool slowly. This should help butthe problem probably comes from powder with moisture in it or the powder wasn't ground fine enough to begin with. You may have oils on the surface even after cleaning,simple solution is hang the part in the oven while it preheats then once up to temperature remove the part,allow to cool then apply powder.
        Let us know how it turns out.


        • #5
          I gave it another shot today on a different part...its a stamped steel part.

          I do have a water seperator in the airline before the gun.

          I went through the same prep process of going to bare metal and ending in 220 grit sanding finish.

          I heated the part with my hand held heat gun first, and then coated the part with the same black powder.

          This time, I put the powder on about 3 times as thick as I was previously.

          I set the oven temp to about 375 and baked the part for 20 minutes. Shut the oven off, propped the door and let cool.

          I got much better results this time. The finish was a little "Wavy" but much improved over my previous attempts.

          As a second attempt, I sanded the finish with 400 wet and applied another coat of the black....laying it on thick.

          I used the same oven cure process, 375 for 20 mins) and I got good results again. Not a perfect smooth finish..... still a little wavy...but
          I think I am on the right track.

          Thanks for the comments....and if you have any other ideas or tips please let me know.



          • #6
            Do you guys polish and wet-sand your finishes to get them mirror like?

            If so what do you use?